The present invention relates to the art of forced draft water and space heating apparatus and, more particularly, to an improved condensate trap for such apparatus.
A condensate trap in accordance with the present invention finds particular utility in conjunction with the disposal of condensate flowing with exhaust gases through the exhaust gas conduit of a forced draft water heater and, accordingly, the invention will be disclosed and described in detail herein in connection with such a water heater. At the same time, it will be understood that the condensate trap can be used with other types of forced draft apparatus, such as space heaters, and with forced draft water heaters other than that with which the trap is disclosed herein.
It is of course well known in connection with forced draft water and space heating apparatus that the products of combustion in flowing through a heat exchanger in the apparatus transfer heat to a fluid medium surrounding the heat exchanger and, in doing so, are cooled, whereby liquid condensate will form during the heat extraction process. The condensate is collected and directed from the heat exchanger to a drain or the like and, typically, such disposal of the condensate has been achieved heretofore through the use of a standard U-type drain trap such as that illustrated, for example, in U.S. Pat. No. 4,541,410. The purpose of the trap is to provide for the disposal of condensate and, at the same time, preclude the escape of exhaust gases through the condensate trap. However, if the apparatus is not used for long periods of time, the condensate in the trap can evaporate and this results in the undesired escape of exhaust gases through the trap. Such U-type trap arrangements are also disadvantageous for the reason the legs of the U have to be of considerable length to preclude the condensate being blown from the trap to the drain conduit by the pressure of the exhaust gases. More particularly in this respect, it will be appreciated that the required length of the legs of the U is dependent on the exhaust gas pressure and, accordingly, increases as the exhaust pressure increases, whereby a considerably long trap may be required to preclude the condensate being blown from the trap.
Another disadvantage of U-type traps in connection with forced draft apparatus of the foregoing character is the fact that the drain tube is relatively small in diameter, whereby the bridging portion of the U between the upwardly extending legs thereof can readily become blocked by the accumulation and hardening of minerals and other contaminates in the water which settle therein and harden during periods of non-use. Accordingly, care must be taken to periodically clean the trap to preclude blockage thereof, which blockage would cause the condensate to backup into the exhaust gas conduit. In fact, to preclude potential damage to the heating apparatus as the result of such a condition, it is contemplated in U.S. Pat. No. 4,729,328 to provide a float valve in the condensate trap which will shut down the heating apparatus in the event of blockage of condensate flow through the exhaust line.
Another arrangement heretofore provided for controlling condensate flow is disclosed in U.S. Pat. No. 4,449,484 wherein a solenoid valve is provided for a condensate collector to provide for the discharge of condensate therefrom following operation of the heating apparatus. The valve remains open when the apparatus is shut down and closes when the apparatus is in operation, whereby condensate is collected without discharge during operation of the apparatus. In addition to the cost of installing, maintaining and operating such a solenoid valve in conjunction with the apparatus, there is the potential during operation of the apparatus for a sufficient quantity of condensate to accumulate in the collector to the level of the exhaust conduit and, therefore, either be blown through the latter with the exhaust gases, or block the exhaust passage to the flow of exhaust gases, both of which are undesirable and potentially dangerous conditions. Furthermore, should the normally open valve fail to close when the apparatus is in operation, exhaust gases are undesirably free to flow through the condensate outlet.